CO₂ gas shielded welding can be divided into automatic and semi-automatic welding according to the operation method, and into fine-wire and thick-wire welding according to the wire diameter used. Fine-wire welding uses a wire diameter of less than 1.6 mm and is suitable for thin-plate welding. Thick-wire welding uses a wire diameter of 1.6 mm or greater and is suitable for medium-to-thick plate welding.
Advantages: CO₂ gas shielded welding offers many benefits compared to shielded metal arc welding (SMAW) and submerged arc welding (SAW).
(1) High welding productivity
In CO₂ gas shielded welding, the current density is high, the melting speed is fast, and there is no need for slag removal during the welding process. Its productivity is 2 to 4 times higher than that of ordinary SMAW.
(2) Low welding distortion
Due to the high current density, concentrated arc heat, narrow heating zone, and the cooling effect of CO₂ gas, welding distortion is minimal. This is especially beneficial for thin-plate welding, as it reduces the need for distortion correction.
(3) Low sensitivity to oil and rust
CO₂ gas decomposes at high temperatures, producing a strong oxidizing effect, making it less sensitive to oil, rust, and other contaminants on the workpiece. Therefore, pre-weld cleaning requirements are not stringent; as long as there is no obvious yellow rust, cleaning is generally unnecessary.
(4) Low hydrogen content in the weld
The shielding gas has strong oxidizing properties at high temperatures, which gives it a high affinity for hydrogen, thereby reducing the hydrogen content in the weld and preventing hydrogen porosity. Additionally, the tendency for cold cracking is lower when welding low-alloy high-strength steels.
(5) Good arc visibility and simple operation
The arc in CO₂ gas shielded welding is highly visible, making it easy to aim and observe the weld. The process is simple to operate and easy to learn, simplifying welder training.
(6) Low cost
CO₂ gas is widely available, inexpensive, and consumes less welding electrical energy, resulting in a low overall cost. Typically, the cost of CO₂ gas shielded welding is 40%–50% of that of SMAW.
Disadvantages
(1) Significant spatter and poor surface appearance
If welding parameters are not properly selected, spatter can be considerable, increasing post-weld cleaning work. However, when parameters are chosen correctly, the spatter produced is less than that of welding with basic electrodes in SMAW. Therefore, this is not considered a major drawback.
(2) Intense arc light
The arc light in CO₂ gas shielded welding is very strong, requiring enhanced personal protection during operation.
(3) Poor wind resistance
When performing CO₂ gas shielded welding outdoors, necessary wind protection measures must be taken.
(4) Limited flexibility
The welding torch and wire feed hose are relatively heavy, making operation less flexible in confined spaces-especially when using a water-cooled torch. In addition, the push-type wire feed hose has a limited length, generally around 3 meters, which imposes certain constraints when welding large workpieces.
(5) Narrow range of weldable materials
CO₂ gas shielded welding cannot be used for stainless steel or easily oxidized non-ferrous metals.
(6) Relatively complex welding equipment
The equipment for CO₂ gas shielded welding is more complex than that for arc welding, with a higher price and greater technical requirements for equipment maintenance.
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